Hybrid-vehicle system

ABSTRACT

A hybrid-vehicle system includes an internal combustion engine configured to deliver a first rotational torque to a crankshaft. The first rotational torque is a maximum torque deliverable by the internal combustion engine. The hybrid-vehicle system also includes a transmission selectively rotatably coupled to the crankshaft, and an assembly including an electric machine rotatably coupled to the transmission and configured to deliver a second rotational torque directly to the transmission. The assembly also includes a one-way clutch configured to rotationally couple the crankshaft and the transmission. The assembly further includes a friction clutch moveable between an engaged state where the crankshaft and the transmission are rotationally coupled, and a disengaged state where the crankshaft and the transmission are rotationally decoupled. The friction clutch is further defined as a latching friction clutch.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to a hybrid-vehicle system and a method for controlling an assembly for a hybrid-vehicle system.

2. Description of the Related Art

Hybrid-vehicle systems for vehicles include an internal combustion engine and an electric motor. In these hybrid-vehicle systems, both the internal combustion engine and the electric motor are capable of delivering torque to wheels of the vehicle to propel the vehicle. Commonly, the internal combustion engine and the electric motor are capable of delivering the torque to a transmission, which, in turn, delivers the torque to the wheels of the vehicle. Hybrid-vehicle systems also commonly include an assembly to selectively transmit the torque from the internal combustion engine and/or the electric motor to the transmission.

The assemblies common to hybrid-vehicle systems typically include a clutch moveable between engaged and disengaged states to selectively transmit the torque from the internal combustion engine and/or the electric motor to the transmission. The clutch must be continuously held in the engaged state to transmit the torque from the internal combustion engine and/or the electric motor through the friction clutch to the transmission, thus requiring continuous use of electric and/or hydraulic power to continuously hold the friction clutch in the engaged state. The continuous use of electric and/or hydraulic power increases the energy consumption of the assembly, increases the cost to operate the assembly, and increases the possibility of failure of the assembly.

As such, there remains a need to provide an improved assembly for a hybrid-vehicle system.

SUMMARY OF THE INVENTION AND ADVANTAGES

A hybrid-vehicle system for a vehicle is disclosed. The hybrid-vehicle system includes an internal combustion engine including a crankshaft. The internal combustion engine is configured to deliver a first rotational torque to the crankshaft. The hybrid-vehicle system also includes a transmission selectively rotatably coupled to the crankshaft of the internal combustion engine. The hybrid-vehicle system further includes an assembly.

The assembly includes an electric machine rotatably coupled to the transmission, and the electric machine is configured to deliver a second rotational torque directly to the transmission in conjunction with the first rotational torque from the internal combustion engine or independent of the first rotational torque from the internal combustion engine. The assembly also includes a one-way clutch coupled to the crankshaft, and the one-way clutch is configured to rotationally couple the crankshaft and the transmission to selectively deliver rotational torque from the crankshaft through the one-way clutch to the transmission. The assembly further includes a friction clutch coupled to the crankshaft, and the friction clutch is moveable between an engaged state and a disengaged state.

When the friction clutch is in the engaged state, the crankshaft and the transmission are rotationally coupled to selectively deliver a portion of the first rotational torque from the crankshaft through the friction clutch to the transmission. When the friction clutch is in the disengaged state, the crankshaft and the transmission are rotationally decoupled and the first rotational torque from the crankshaft is not transmitted through the friction clutch. The friction clutch is further defined as a latching friction clutch.

The movement of the friction clutch between the engaged and disengaged states to rotationally couple and selectively deliver the portion of the first rotational torque from the crankshaft through the friction clutch to the transmission is optimally accomplished due to the ability of the friction clutch to smoothly engage and disengage. Thus, the friction clutch prevents damage to the assembly, the internal combustion engine, and/or the electric machine during engagement of the friction clutch. The friction clutch also produces a smooth driving experience of the vehicle.

The latching friction clutch is able to remain in the engaged state without additional power consumption, such as hydraulic power consumption or electrical power consumption. As such, the latching friction clutch results in low power consumption during steady-state operation of the internal combustion engine without sacrificing delivery of the torque to the transmission. Additionally, the latching friction clutch may allow the one-way clutch to be configured to deliver less than 100% of the first rotational torque to the transmission because the latching friction clutch may deliver the portion of the first rotational torque from the crankshaft through the latching friction clutch to the transmission without adversely affecting power consumption of the hybrid-vehicle system.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1A is a schematic illustration of a hybrid-vehicle system having an internal combustion engine, an electric machine, a transmission, a latching friction clutch in a disengaged state, and a one-way clutch;

FIG. 1B is a schematic illustration of the hybrid-vehicle system, with the latching friction clutch in an engaged state;

FIG. 2A is a schematic illustration of the hybrid-vehicle system, with the latching friction clutch in the disengaged state, and with the one-way clutch having a one-way clutch output that is rotationally coupled to the transmission without being rotationally coupled to the electric machine; and

FIG. 2B is a schematic illustration of the hybrid-vehicle system, with the latching friction clutch in the engaged state.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the Figures, wherein like numerals indicate like parts throughout the several views, a hybrid-vehicle system 10 for a vehicle is shown schematically in FIGS. 1A-2B. The hybrid-vehicle system 10 includes an internal combustion engine 12 including a crankshaft 14. The internal combustion engine 12 is configured to deliver a first rotational torque to the crankshaft 14. The first rotational torque may be a maximum torque deliverable by the internal combustion engine 12.

The internal combustion engine 12 has a cylinder and a piston disposed in the cylinder. During operation of the internal combustion engine 12, the piston is moved by combustion in the cylinder, which then rotates the crankshaft 14 and delivers a torque to the crankshaft 14. The hybrid-vehicle system 10 also includes a transmission 16 selectively rotatably coupled to the crankshaft 14 of the internal combustion engine 12. The hybrid-vehicle system 10 further includes an assembly 18.

The assembly 18 includes an electric machine 20 rotatably coupled to the transmission 16, and the electric machine 20 is configured to deliver a second rotational torque directly to the transmission 16 in conjunction with the first rotational torque from the internal combustion engine 12 or independent of the first rotational torque from the internal combustion engine 12. Although not required, the electric machine 20 may be an electric motor configured to convert electrical energy into rotational energy and torque, and/or may be an electric generator configured to convert rotational energy and torque into electrical energy. The assembly 18 also includes a one-way clutch 22 coupled to the crankshaft 14. The one-way clutch 22 is configured to rotationally couple the crankshaft 14 and the transmission 16 to selectively deliver rotational torque from the crankshaft 14 through the one-way clutch 22 to the transmission 16. The assembly 18 further includes a friction clutch 24 coupled to the crankshaft 14. The friction clutch 24 is moveable between an engaged state and a disengaged state.

When the friction clutch 24 is in the engaged state, as shown in FIGS. 1A and 2A, the crankshaft 14 and the transmission 16 are rotationally coupled to selectively deliver a portion of the first rotational torque from the crankshaft 14 through the friction clutch 24 to the transmission 16. When the friction clutch 24 is in the disengaged state, as shown in FIGS. 1B and 2B, the crankshaft 14 and the transmission 16 are rotationally decoupled and the first rotational torque from the crankshaft 14 is not transmitted through the friction clutch 24. The friction clutch 24 is further defined as a latching friction clutch 26.

The movement of the latching friction clutch 26 between the engaged and disengaged states to rotationally couple and selectively deliver a portion of the first rotational torque from the crankshaft 14 through the latching friction clutch 26 to the transmission 16 is optimally accomplished due to the ability of the latching friction clutch 26 to smoothly engage and disengage. The friction clutch 24 is able to smoothly engage and disengage because the friction clutch 24 has at least one friction plate able to partially engage while moving between the disengaged and engaged states. Partial engagement of the friction plate prevents abrupt transmission of the torque from the crankshaft 14 to the transmission 16. Thus, the latching friction clutch 26 prevents damage to the assembly 18, the internal combustion engine 12, and/or the electric machine 20 during engagement of the latching friction clutch 26. The latching friction clutch 26 also produces a smooth driving experience of the vehicle.

The latching friction clutch 26 is able to remain in the engaged state without additional power consumption, such as hydraulic power consumption or electrical power consumption. As such, the latching friction clutch 26 results in low power consumption during steady-state operation of the internal combustion engine 12 without sacrificing delivery of the torque to the transmission 16. Additionally, the latching friction clutch 26 may allow the one-way clutch 22 to be configured to deliver less than 100% of the first rotational torque to the transmission 16 because the latching friction clutch 26 may deliver the portion of the first rotational torque from the crankshaft 14 through the latching friction clutch 26 to the transmission 16 without adversely affecting power consumption of the hybrid-vehicle system 10.

Typically, the latching friction clutch 26 has a latch 38 configured to prevent the latching friction clutch 26 from moving from the engaged state to the disengaged state. The latch 38 may be mechanical, such as a ball-and-spring detent, a pawl or rachet, a plug disposed in a fluid flow path defined in the latching friction clutch 26, a separator plate disposed between friction plates and configured to engage a housing or another plate to remain in the engaged state, or a hydraulic or electric piston coupled to the separator plate and/or the friction plates and configured to engage the housing or another plate to remain in the engaged state. Although not required, when the latch 38 is a ball-and-spring detent, the ball in the engaged state is disposed in one or more of a groove, recess, depression, indentation, or the like of the housing, the hydraulic or electric piston, the separator plate, or another plate.

The latching friction clutch 26 and the one-way clutch 22 are disposed in parallel with one another. Said differently, the torque from the crankshaft 14 may be delivered through the latching friction clutch 26 to the transmission 16, the torque from the crankshaft 14 may be delivered through the one-way clutch 22 to the transmission 16, or the torque from the crankshaft 14 may be delivered through both the latching friction clutch 26 and the one-way clutch 22 to the transmission 16.

During start-up of the internal combustion engine 12, the crankshaft 14 begins rotating at a rotational speed. During start-up of the internal combustion engine 12, the electric machine 20 may be required to supplement the torque delivered by the crankshaft 14 of the internal combustion engine 12. For the electric machine 20 to supplement the torque delivered by the crankshaft 14 of the internal combustion engine 12, the electric machine must be synchronized with the rotational speed of the crankshaft 14. To synchronize the rotational speed of the crankshaft 14 and the electric machine 20, the latching friction clutch 26 may be moved from the disengaged state to the engaged state to smoothly rotational couple the crankshaft 14 and the electric machine 20. The latching friction clutch 26 is able to synchronize the rotation of the crankshaft 14 and the electric machine 20 without aid from any external devices.

After the latching friction clutch 26 is in the engaged state and the rotation of the crankshaft 14 and the electric machine 20 are synchronized, the one-way clutch 22 may be moved from the disengaged state to the engaged state to provide additional capacity to deliver the torque from the internal combustion engine 12 to the transmission 16. Because the rotational speed of the crankshaft 14 and the electric machine 20 are already synchronized and the crankshaft 14 and the electric machine 20 are already rotationally coupled, the engagement of the one-way clutch 22 can be accomplished without rough transmission of the torque to the transmission 16, avoiding potential damage to the assembly 18, the internal combustion engine 12, and/or the electric machine 20.

It is to be appreciated that the crankshaft 14 and the electric machine 20 are not required to be at the same rotational speed relative to one another to move the one-way clutch 22 from the disengaged state to the engaged state. As the latching friction clutch 26 is engaged, a differential in rotational speed between the crankshaft 14 and the electric machine 20 is decreased. This decrease in the differential in rotational speed between the crankshaft 14 and the electric machine 20 may also allow the one-way clutch 22 to be moved to the engaged state without rough transmission of the torque to the transmission 16, and may also avoid potential damage to the assembly 18, the internal combustion engine 12, and/or the electric machine 20.

After the one-way clutch 22 is moved from the disengaged state to the engaged state, the latching friction clutch 26 may be moved from the engaged state to the disengaged state to reduce power consumption of the hybrid-vehicle system 10. More specifically, the hybrid-vehicle system 10 may include a pump to hydraulically actuate the latching friction clutch 26 to hold the latching friction clutch 26 in the engaged state, may include a solenoid to electrically actuate the latching friction clutch 26 to hold the latching friction clutch 26 in the engaged state, or may include an electric motor and, optionally, a gear, a lever, a ramp, or a series of gears, levers, and/or ramps to change the torque ratio of the electric motor and to hold the latching friction clutch 26 in the engaged state. To move the latching friction clutch 26 from the engaged state to the disengaged state, the pump, solenoid, and/or electric motor are turned off, thus reducing power consumption of the hybrid-vehicle system 10. Alternatively, the latching friction clutch 26 may remain in the engaged state to provide capacity beyond the capacity of the one-way clutch 22 to deliver the torque to the transmission 16.

Beyond propelling the vehicle, the latching friction clutch 26 while in the engaged state may allow negative torque transmission from the internal combustion engine 12. Negative torque transmission is transmission of torque in an opposite rotational direction as typical during operation of the internal combustion engine 12 (e.g. counterclockwise if normally clockwise, or clockwise if normally counterclockwise). The negative torque transmission may be used to slow the vehicle without the aid of external brakes. Without the latching friction clutch 26 allowing the negative torque transmission, the one-way clutch 22 would overrun.

The hybrid-vehicle system 10 may also include a damper 28 coupled to the crankshaft 14 of the internal combustion engine 12 and both the latching friction clutch 26 and the one-way clutch 22 of the assembly 18. The damper 28 may be, but is not limited to, a harmonic damper, a centrifugal pendulum absorber, or a dual mass flywheel. The hybrid-vehicle system 10 may further include a transmission launch device coupled to the transmission 16 and to both the latching friction clutch 26 and the one-way clutch 22. The transmission launch device may be, but is not limited to, a torque converter or a launch clutch.

In some embodiments, in the engaged state, the latching friction clutch 26 is limited to delivering 85% or less of the first rotational torque to the transmission 16. In the embodiments where the latching friction clutch 26 is sized such that the latching friction clutch 26 is limited to delivering 85% or less of the first rotational torque to the transmission 16, the size of the assembly 18 is decreased, the cost of the assembly 18 is lowered, and the heat generation caused by the latching friction clutch 26 in the assembly 18 is limited.

Although not required, in one embodiment, the latching friction clutch 26 in the engaged state is limited to delivering 70% or less of the first rotational torque to the transmission 16. It is to be appreciated that the latching friction clutch 26 may be limited to delivering 50% or less of the first rotational torque to the transmission 16, may be limited to delivering 40% or less of the first rotational torque to the transmission 16, may be limited to delivering 30% or less of the first rotational torque to the transmission 16, and/or may be limited to delivering 20% or less of the first rotational torque to the transmission 16.

The particular percentage of the first rotational torque at which the latching friction clutch 26 is limited to delivering may be determined by, but is not limited to, the torque from the internal combustion engine 12 between start-up of the internal combustion engine 12 and the torque at which the rotational speed of the crankshaft 14 and the electric machine 20 are synchronized. This torque is typically less than the first rotational torque, which is the maximum torque deliverable by the internal combustion engine 12.

In some embodiments, the one-way clutch 22 is configured to deliver at least 100% of the first rotational torque from the crankshaft 14 to the transmission 16. In the embodiments where the one-way clutch 22 is configured to deliver at least 100% of the first rotational torque from the crankshaft 14 to the transmission 16, the one-way clutch 22 is able to be in an engaged state during steady-state operation of the internal combustion engine 12 while the latching friction clutch 26 is in the disengaged state while not limiting the amount of the first rotational torque able to be delivered to the transmission 16. In other words, in these embodiments, the one-way clutch 22 is able to deliver all of the first rotational torque from the internal combustion engine 12 to the transmission 16 without assistance from the latching friction clutch 26. It is to be appreciated that the one-way clutch 22 may be configured to deliver more than the first rotational torque to the transmission 16. Said differently, the one-way clutch 22 may be over-sized such that a safety margin exists to ensure that all of the first rotational torque may be delivered by the one-way clutch 22.

Alternatively, the one-way clutch 22 may be configured to deliver less than 100% of the first rotational torque from the crankshaft 14 to the transmission 16. In this embodiment, the one-way clutch 22 in combination with the latching friction clutch 26 is required to deliver the first rotational torque from the internal combustion engine 12 to the transmission 16. Said differently, both the one-way clutch 22 and the latching friction clutch 26 must be in the engaged state to deliver all of the first rotational torque to the transmission 16 in this embodiment.

In some embodiments, in the engaged state, the latching friction clutch 26 and the one-way clutch 22 are together configured to deliver from 90 to 185% of the first rotational torque from the crankshaft 14 to the transmission 16. In other embodiments, in the engaged state, the latching friction clutch 26 and the one-way clutch 22 are together configured to deliver from 95 to 120% of the first rotational torque from the crankshaft 14 to the transmission 16. In these embodiments, the latching friction clutch 26 and the one-way clutch 22 may be both in the engaged state to deliver all of the first rotational torque to the transmission 16. It is to be appreciated that this range is merely exemplary. For example, the latching friction clutch 26 and the one-way clutch 22 may be together configured to deliver less than 90%, or may be together configured to deliver more than 185%, of the first rotational torque to the transmission 16.

In the embodiments where the latching friction clutch 26 and the one-way clutch 22 are together configured to deliver over 100% of the first rotational torque to the transmission 16, an additional percentage over 100% is the safety margin that exists to ensure that all of the first rotational torque is able to be delivered to the transmission 16. The factors that determine the safety margin (i.e., the amount of the additional percentage over 100%) include, but are not limited to, the absolute amount of the first rotational torque and the ability of the one-way clutch 22 and the latching friction clutch 26 to deliver torque relative to one another.

The hybrid-vehicle system 10 may also include a controller 40 configured to change delivery of the first rotational torque to through the one-way clutch 22 to the transmission 16, from through the latching friction clutch 26 to the transmission 16. Said differently, the controller 40 changes delivery of the torque from the latching friction clutch 26 to the one-way clutch 22. The controller 40 may change delivery of the torque upon receiving sensory input of the torque being delivered from the internal combustion engine 12 through the crankshaft 14 to the latching friction clutch 26. It is to be appreciated that the controller 40 may also change delivery of the torque from the one-way clutch 22 to the latching friction clutch 26. In some embodiments, the controller 40 is configured to change delivery of the first rotational torque upon the internal combustion engine 12 reaching a predetermined operating condition. The predetermined operating condition may be, but is not limited to, a portion of the first rotational torque generated by the internal combustion engine 12, and a rotational speed of the crankshaft 14.

In some embodiments, as shown in FIGS. 1A-2B, the latching friction clutch 26 has a friction clutch input 30 that is rotationally coupled to the internal combustion engine 12, and a friction clutch output 32 that is rotationally coupled to the electric machine 20. The friction clutch input 30 and the friction clutch output 32 are rotationally decoupled when the latching friction clutch 26 is in the disengaged state, and the friction clutch input 30 and the friction clutch output 32 are rotationally coupled when the latching friction clutch 26 is in the engaged state.

In one embodiment, as shown in FIGS. 1A and 1B, the one-way clutch 22 has a one-way clutch input 34 that is rotationally coupled to the internal combustion engine 12, and a one-way clutch output 36 that is rotationally coupled to the electric machine 20. In this embodiment, the friction clutch output 32 and the one-way clutch output 36 may be rotationally coupled to one another. It is to be appreciated that the one-way clutch 22 may have a one-way clutch output 36 that is rotationally coupled to the transmission 16 without being rotationally coupled to the electric machine 20, as shown in FIGS. 2A and 2B. In this embodiment, the friction clutch output 32 and the one-way clutch output 36 may be rotationally decoupled from one another.

In one embodiment, the friction clutch input 30 and the one-way clutch input 34 are both rotationally coupled to the internal combustion engine 12, and the friction clutch output 32 and the one-way clutch output 36 are both rotationally coupled to the electric machine 20. In this embodiment, the first rotational torque may be delivered from the internal combustion engine 12 through either the latching friction clutch 26, the one-way clutch 22, or both the latching friction clutch 26 and the one-way clutch 22 to the transmission 16, and the electric machine 20 may deliver the second rotational torque directly to the transmission 16 in conjunction with the first rotational torque from the internal combustion engine 12.

A method for controlling the assembly 18 for the hybrid-vehicle system 10 includes the step of engaging the latching friction clutch 26. The step of engaging the latching friction clutch 26 is accomplished by moving the latching friction clutch 26 from the disengaged state to the engaged state. In the engaged state, the crankshaft 14 and the electric machine 20 are rotationally coupled to deliver rotational torque from the crankshaft 14 through the latching friction clutch 26 to the transmission 16. In the disengaged state, the crankshaft 14 and the electric machine 20 are rotationally decoupled and the first rotational torque from the crankshaft 14 is not transmitted through the latching friction clutch 26. The method also includes the step of latching the friction clutch such that the latching friction clutch remains in the engaged state. The step of latching the latching friction clutch 26 may be accomplished through moving the latch 38 of the latching friction clutch 26, if present. The method also includes the step of engaging the one-way clutch 22 to rotationally couple the crankshaft 14 and the transmission 16 to deliver rotational torque from the crankshaft 14 through the one-way clutch 22 to the transmission 16.

The method may also include the step of disengaging the latching friction clutch 26 by moving the latching friction clutch 26 from the engaged state to the disengaged state. In this embodiment, the one-way clutch 22 may still be in the engaged state and the first rotational torque may be delivered from the internal combustion engine 12 to the transmission 16. In this embodiment, the hybrid-vehicle system 10 has reduced power consumption because the pump and/or solenoid are turned off.

The method may further include the step of delivering the second rotational torque via the electric machine 20 directly to the transmission 16. Delivering the second rotational torque directly to the transmission 16 more efficiently propels the vehicle without being hindered by a damper or additional componentry.

In some embodiments, the step of engaging the latching friction clutch 26 precedes the step of delivering the second rotational torque via the electric machine 20 directly to the transmission 16. In these embodiments, the second rotational torque may be supplemental to the first rotational torque from the internal combustion engine 12. Alternatively, in other embodiments, the step of delivering the second rotational torque via the electric machine 20 directly to the transmission 16 precedes the step of engaging the latching friction clutch 26. In these other embodiments, the electric machine 20 may be operated while the internal combustion engine 12 is not operating.

In some embodiments, the step of delivering the second rotational torque via the electric machine 20 directly to the transmission 16 precedes the step of engaging the one-way clutch 22. In these embodiments, the first rotational torque may be delivered from the internal combustion engine 12 through the latching friction clutch 26 in the engaged state to the transmission, and the electric machine 20 may supplement the first rotational torque by delivering the second rotational torque to the transmission 16. The delivery of the first and second rotational torques may be accomplished during start-up of the internal combustion engine 12 before the one-way clutch 22 is in the engaged state to deliver all of the first rotational torque to the transmission 16.

In some embodiments, the step of delivering the second rotational torque via the electric machine 20 precedes the step of disengaging the latching friction clutch 26. The latching friction clutch 26 may be disengaged during steady-state operation of the internal combustion engine 12 when the first rotational torque is being delivered from the internal combustion engine 12 through the one-way clutch 22 to the transmission 16. As such, the electric machine 20 may be required to deliver the second rotational torque during start-up of the internal combustion engine 12, which precedes the step of disengaging the latching friction clutch 26 during steady-state operation of the internal combustion engine 12.

The method may further include the step of delivering the first rotational torque from the internal combustion engine 12 to the transmission 16. The step of delivering the second rotational torque via the electric machine 20 directly to the transmission 16 may precede the step of delivering the first rotational torque from the internal combustion engine 12 to the transmission 16. In this embodiment, the internal combustion engine 12 is operated before the electric machine 20 is operated.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described. 

What is claimed is:
 1. A hybrid-vehicle system comprising: an internal combustion engine comprising a crankshaft, said internal combustion engine configured to deliver a first rotational torque to said crankshaft; a transmission selectively rotatably coupled to said crankshaft of said internal combustion engine; and an assembly comprising, an electric machine rotatably coupled to said transmission, said electric machine configured to deliver a second rotational torque directly to said transmission in conjunction with said first rotational torque from said internal combustion engine or independent of said first rotational torque from said internal combustion engine; a one-way clutch coupled to said crankshaft, with said one-way clutch configured to rotationally couple said crankshaft and said transmission to selectively deliver rotational torque from said crankshaft through said one-way clutch to said transmission; and a friction clutch coupled to said crankshaft, with said friction clutch moveable between an engaged state where said crankshaft and said transmission are rotationally coupled to selectively deliver a portion of said first rotational torque from said crankshaft through said friction clutch to said transmission, and a disengaged state where said crankshaft and said transmission are rotationally decoupled and said first rotational torque from said crankshaft is not transmitted through said friction clutch, wherein said friction clutch is further defined as a latching friction clutch.
 2. The hybrid-vehicle system as set forth in claim 1, wherein said latching friction clutch has a latch configured to prevent said latching friction clutch from moving from said engaged state to said disengaged state.
 3. The hybrid-vehicle system as set forth in claim 1, wherein said first rotational torque is the maximum torque deliverable by the internal combustion engine, and wherein, in said engaged state, said latching friction clutch is limited to delivering 85% or less of said first rotational torque to said electric machine.
 4. The hybrid-vehicle system as set forth in claim 1, wherein said first rotational torque is the maximum torque deliverable by said internal combustion engine, and wherein, in said engaged state, said latching friction clutch is limited to delivering 50% or less of said first rotational torque to said transmission.
 5. The hybrid-vehicle system as set forth in claim 1, wherein said first rotational torque is the maximum torque deliverable by the internal combustion engine, and wherein said one-way clutch is configured to deliver at least 100% of said first rotational torque from said crankshaft to said transmission.
 6. The hybrid-vehicle system as set forth in claim 1, wherein, in said engaged state, said latching friction clutch and said one-way clutch are together configured to deliver from 90 to 185% of said first rotational torque from said crankshaft to said transmission.
 7. The hybrid-vehicle system as set forth in claim 1 further comprising a controller configured to change delivery of said first rotational torque to through said one-way clutch to said transmission, from through said latching friction clutch to said transmission.
 8. The hybrid-vehicle system as set forth in claim 8, wherein the controller is configured to change delivery of said first rotational torque upon the internal combustion engine reaching a predetermined operating condition.
 9. The hybrid-vehicle system as set forth in claim 1, wherein said latching friction clutch has a friction clutch input that is rotationally coupled to said internal combustion engine, and a friction clutch output that is rotationally coupled to said electric machine.
 10. The hybrid-vehicle system as set forth in claim 1, wherein said one-way clutch has a one-way clutch input that is rotationally coupled to said internal combustion engine, and a one-way clutch output that is rotationally coupled to said electric machine.
 11. The hybrid-vehicle system as set forth in claim 1, wherein said latching friction clutch has friction clutch input and a friction clutch output, and said one-way clutch has one-way clutch input and a one-way clutch output, wherein said friction clutch input and said one-way clutch input are both rotationally coupled to said internal combustion engine, and wherein said friction clutch output and said one-way clutch output are both rotationally coupled to said electric machine.
 12. An assembly for use in a hybrid-vehicle system, with the hybrid-vehicle system including an internal combustion engine including a crankshaft, the internal combustion engine configured to deliver a first rotational torque to the crankshaft, and a transmission adapted to be selectively rotatably coupled to the crankshaft for transmitting rotational torque via said assembly, said assembly comprising: an electric machine adapted to be rotatably coupled to the transmission, said electric machine configured to deliver a second rotational torque directly to the transmission in conjunction with the first rotational torque from the internal combustion engine or independent of the first rotational torque from the internal combustion engine; a one-way clutch coupled to the crankshaft, with said one-way clutch configured to rotationally couple the crankshaft and the transmission to selectively deliver rotational torque from the crankshaft through said one-way clutch to the transmission; and a friction clutch adapted to be coupled to the crankshaft, with said friction clutch moveable between an engaged state where the crankshaft and said electric machine are adapted to be rotationally coupled to selectively deliver a portion of the first rotational torque from the crankshaft through said friction clutch to the transmission, and a disengaged state where the crankshaft and said electric machine are adapted to be rotationally decoupled and the first rotational torque from the crankshaft is not transmitted through said friction clutch, wherein said friction clutch is further defined as a latching friction clutch.
 13. A method for controlling an assembly for a hybrid-vehicle system, with the hybrid-vehicle system including an internal combustion engine including a crankshaft, the internal combustion engine configured to deliver a first rotational torque to the crankshaft, and a transmission adapted to be selectively rotatably coupled to the crankshaft for transmitting rotational torque via the assembly, the assembly including an electric machine rotatably coupled to the transmission, the electric machine configured to deliver a second rotational torque directly to the transmission in conjunction with the first rotational torque from the internal combustion engine or independent of the first rotational torque from the internal combustion engine, a one-way clutch coupled to the crankshaft, and a latching friction clutch coupled to the crankshaft; said method comprising the steps of: engaging the latching friction clutch by moving the latching friction clutch to an engaged state where the crankshaft and the electric machine are rotationally coupled to deliver rotational torque from the crankshaft through the latching friction clutch to the transmission from a disengaged state where the crankshaft and the electric machine are rotationally decoupled and the first rotational torque from the crankshaft is not transmitted through the latching friction clutch, latching the latching friction clutch such that the latching friction clutch remains in the engaged state, and engaging the one-way clutch to rotationally couple the crankshaft and the transmission to deliver rotational torque from the crankshaft through the one-way clutch to the transmission.
 14. The method as set forth in claim 14 further comprising the step of disengaging the latching friction clutch by moving the latching friction clutch from the engaged state to the disengaged state.
 15. The method as set forth in claim 14, wherein the latching friction clutch is configured to deliver 85% or less of the first rotational torque from the crankshaft to the electric machine through the latching friction clutch.
 16. The method as set forth in claim 14 further comprising the step of disengaging the friction clutch by moving the friction clutch from the engaged state to the disengaged state.
 17. The method as set forth in claim 14 further comprising the step of delivering the second rotational torque via the electric machine directly to the transmission.
 18. The method as set forth in claim 16, wherein the step of engaging the friction clutch precedes the step of delivering the second rotational torque via the electric machine directly to the transmission.
 19. The method as set forth in claim 16, wherein the step of delivering the second rotational torque via the electric machine directly to the transmission precedes the step of engaging the one-way clutch. 